<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>三角形</title>
    <style type="text/css">
        div {
            width: 0;
            height: 0;
            border: 100px solid black;
            border-left-color: black;
            border-top-color: transparent;
            border-right-color: transparent;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>